The religion was probably based on ancestor worship.
The West Kennet long barrow is a chambered tomb dating from 3500 BC. It was in use until 2200BC, when it was sealed with chalk rubble and the gigantic sarsen boulders that now guard the entrance.
Excavations in 1955-56 found at least 46 burials, ranging from babies to elderly persons. The bones were disarticulated with some of the skulls and long bones missing. It has been suggested that the bones were removed periodically for display or transported elsewhere with the blocking facade being removed and replaced each time.
(from various sources)